The present invention relates to the art of portable emergency breathing apparatus and, more particularly, to improvements in connection with breathing apparatus of the character in which breathing gas from a source is continuously supplied at a controlled rate to the user.
Breathing apparatus of the character in which oxygen from a source such as a compressed oxygen container is continuously supplied at a controlled rate to a hood or face mask worn by the user is generally referred to as open circuit apparatus in that the gas breathed by the user from the tank is exhaled to atmosphere. Such exhaling to atmosphere distinguishes the open circuit apparatus from apparatus generally known as closed circuit apparatus wherein the exhaled breath of the user is mixed with oxygen from a supply container, scrubbed to reduce the concentration of exhaled carbon dioxide, and re-breathed by the user. While closed circuit apparatus has the advantage of optimizing the duration of use with a given sized oxygen supply container, such apparatus is expensive, bulky and has exposed component parts which are subject to easy damage whereby they are undesirable in certain environments of potential use such as in airplanes, for example, where a large number of units must be stored and storage space is at a premium and where the total weight of the units to be stored is a major consideration. A major disadvantage of open circuit apparatus heretofore available has been the size of the breathing gas supply container or containers necessary to provide a given duration of use. Thus, while open circuit units have fewer component parts and may be less expensive, the same problems with respect to acceptance of the apparatus in a given environment exists with respect to the size and weight of a unit. In addition to the foregoing disadvantages of a closed circuit system, there are potential life endangering situations wherein the longer duration provided by such apparatus is not necessary, whereby the use of the shorter duration but less expensive open circuit apparatus could be acceptable and possibly preferable. It remains, however, that with the open circuit apparatus heretofore available the overall size and weight of the apparatus necessary to provide a given duration of use is excessive and does not resolve the problems encountered in connection with use in environments wherein weight and storage space are major concerns.